function G=d2func(x, y)
% It's Rosenbrock's Hessian.
G = zeros(2, 2);
G(1, 1) = 1200.0 * x.^2 - 400.0 * y + 2.0;
G(1, 2) = -400.0 * x;
G(2, 1) = G(1, 2);
G(2, 2) = 200.0;